The objective of this study is to determine the importance of histocompatibility (HL-A) antigens in corneal transplantation. In kidney transplants the improved success has been partially attributed to matching of transplantation antigens of the donor and the recipient. In addition, recent data from kidney transplants and preliminary data from corneal transplants indicate that presensitization of the recipient to HL-A antigens in the form of lymphocytotoxic (anti-HL-A) antibodies predisposes to immune graft rejection. In this study the HL-A antigen type of all donors and recipients for corneal transplantation will be determined. Prospective recipients will be screened for lymphocytotoxic antibodies. Cross-match tests between serum of sensitized patients and cells of the donor will be performed, and attempts will be made to avoid HL-A antigen mismatches of the same specificity as the lymphocytotoxic antibodies of the recipient. Postoperativel serum and lymphocytes of the recipient will be tested at intervals against cryopreserved lymphocytes and cultured corneal cells of the donor to detect development of cell mediated and/or humoral immunity.